Infusion pumps are typically used to regulate the delivery of fluids, which may include potentially hazardous drugs, to a patient with a high degree of accuracy. Ordinarily, a roller clamp is moved to a closed position to stop flow through IV tubing before the tubing is removed from an infusion pump in order to prevent a situation that is sometimes referred to as "free flow" or "fluid runaway", that is, where the fluid is free to flow rapidly through the IV tubing without regulation by the infusion pump. Such roller clamps are effective in preventing free flow only when they are manually moved to their closed positions, and free flow or fluid runaway may occur if the roller clamp is inadvertently left in its open position. As a result, an automatic free flow prevention system is now desired wherein fluid runaway is prevented regardless of whether the pump operator remembers to close a roller or slide clamp.
One approach is described in coassigned U.S. Pat. No. 4,585,441 wherein an interlock is provided to prevent removal of the IV set unless fluid flow through the tubing is stopped. The pump operator must manually close a clamp to stop fluid flow through the tubing before the infusion pump will permit removal of the IV set.
A permanent clamp may be provided on the infusion pump from which the IV set must be manually disconnected during removal of the IV set from the infusion pump. That approach reduces the risk of fluid runaway because the permanent clamp reduces the possibility of thoughtless removal of the IV set from the infusion pump. The act of disconnecting the IV set from the permanent clamp tends to remind the operator of the need to close the roller or slide clamp on the IV set; however, it does not eliminate the risk that the operator will remove the IV set without first closing this clamp.
Other approaches include employing slide clamps to prevent or reduce the risk of removing the IV set without closing a clamp. U.S. Pat. Nos. 4,586,691; 4,689,043; and 4,818,190 describe employing slide clamps to prevent fluid runaway during removal of IV sets from infusion pumps.
Coassigned U.S. Pat. No. 5,017,192 describes a flexible clamp having a pair of clamping arms that are biased to a closed position to close the lumen of IV tubing. The clamping arms are moved and held in an open position by a wedge in the infusion pump to permit flow through the tubing during operation of the infusion pump. The clamping arms of the flexible clamp automatically close the tubing when the IV tubing set is removed from the infusion pump.